1. Field of the Invention
The present invention generally relates to cordless telephones and, more particularly, to a cordless telephone in which a battery incorporated therein can be prevented from being consumed uselessly and in which a telephone line network can be prevented from being captured meaninglessly.
2. Description of the Prior Art
In a standard telephone set, the user can dial a number for making an outgoing call or can receive an incoming call by only picking up a transmitter and receiver from the telephone body.
Incidentally, when the user receives an incoming call by the cordless telephone, the following operations are needed:
(1) hold a handset unit (remote station) in one's hand, and
(2) depress a talk button. This depression of the talk button opens a communication channel between the handset unit and a base unit (master station) and also connects the base unit to the telephone line network.
When the user wants to make an outgoing call, after the above operations (1) and (2) the user has to dial the phone number of the other party (3).
These operations are cumbersome for the user and make the cordless telephone inconvenient as compared with a standard telephone set in which the user can make an outgoing call and receive an incoming call only by picking up the transmitter and receiver from the standard telephone set.
To remove such disadvantages, a proposed cordless telephone has a special function which might be called a "quick talk" function. This type of cordless telephone having such quick talk function will be explained hereinafter.
The handset unit of the cordless telephone system generally incorporates therein a rechargeable battery as an operation power source so that the base unit has a charging circuit therein or a special charging stand is provided for charging the battery of the handset unit. When the handset unit is not in use, the handset unit is set in the base unit at its predetermined charging position or the handset unit is placed in the charging stand. Then, in this condition, a charging current flows to the battery incorporated within the handset unit so that the handset unit is placed in the standby mode on the basis of a detected output of the charging current, and so that the base unit also is placed in the standby mode.
When the user wants to make an outgoing call or the user wants to receive an incoming call, the user picks up the handset unit from the base unit or from the charging stand. Then, the charging current is inhibited from flowing to the handset unit and a process corresponding to "depress a talk button" in the above-mentioned item (2) is performed in the handset unit on the basis of the detected output, so that a communication channel is opened between the handset unit and the base unit and the base unit is connected to the telephone line network.
If the cordless telephone system has such quick talk function, the cordless telephone can be utilized as the standard telephone set while the advantages of the cordless telephone are still maintained.
Incidentally, in the cordless telephone having the above-mentioned quick talk function, if the user picks up the handset unit from the base unit for reasons than telephone conversation, such as when the user picks up the handset unit to clean the smudged handset unit and when the user picks up the handset unit to register an abbreviated phone number in the handset unit, the communication channel is unavoidably opened between the handset unit and the base unit and also the base unit is unavoidably connected to the telephone line network, so that the battery of the handset unit is consumed uselessly. Furthermore, the telephone line network is occupied meaninglessly (the telephone line network is captured uselessly), which causes trouble in the telephone office and which hinders the cordless telephone from receiving an incoming call.
Furthermore, when the handset unit is unintentionally knocked down from or disengaged from the base unit or from the charging stand due to some vibration or the like, similar problems will arise.